A cookware unit may be employed as any one or all of the following: for heating, cooling, storing, serving and/or transporting food contents. Cookware units are generally composed of a container, with or without handle, the protective non-stick or decorative coatings of the container, the closure of the container and the coatings of the closure. According to the present state of art, the handle of the container, the closure of the cookware unit and the entire container with all its coatings must generally be discarded when any one of them has deteriorated or has been damaged, particularly where the container is part of a matched set which has been discontinued.
The most vulnerable, the most short lived and most expensive coating of the cookware unit is the interior non-stick coating of the container. Due to the inherent limitations of non-stick coating materials in their resistance to wear, their life is normally limited to approximately 2 to 3 years. The container itself, however, which is usually formed of strong metals, has the potential to serve a user for his entire lifetime. Nevertheless, the present state of art necessitates the replacement of the entire container each time its non-stick coating is damaged or reaches the end of its useful life. This invention relates to a cookware unit, and more particularly, a container of a cookware unit having a replaceable infix or insert member.
Cookware containers having non-stick coatings, such as PTFE, are well known in the cookware field. Such containers are generally formed of solid aluminum and the interior aluminum surface which contacts the food to be prepared is coated with a suitable non-stick coating. Prior to the application of the non-stick coating, the aluminum surface of these containers must first be prepared by suitable methods in order to insure adequate adhesion between the non-stick coating and the aluminum. Such methods include etching, either chemically or mechanically, or the application of a sintered ceramic anchor frit which is heat bonded to the aluminum and to which, in turn, the non-stick coating is bonded. Either where the aluminum is etched or where the sinter bonded anchor frit is applied, the thickness of the aluminum must be substantially increased relative to the thickness which would otherwise be satisfactory where non-stick coatings are not employed. If the aluminum is etched, the increased thickness is necessary to insure that adequate container strength remains after the extensive metal erosion attendant to the etching. On the other hand, where a heat bonded anchor frit is employed, the container thickness must also be increased to compensate for the loss of strength which results from the annealing of the aluminum which occurs when the container is raised to the temperatures necessary to bond such anchor frits to the metal substrate, these temperatures frequently being in excess of 1000.degree.F.
In my copending United States application for Letters Patent, Ser. No. 3,044, filed Jan. 15, 1970 now U.S. Pat. No. 3,788,513, a laminated cookware construction is disclosed in which heat bonded anchor frits and non-stick coatings may be employed while actually realizing a decrease in the amount of relatively expensive aluminum necessary in such non-stick cookware containers from that previously required. Similarly to the invention disclosed in the aforementioned application, the present invention also has as an important object, the substantial reduction in the amount of relatively expensive aluminum materials in non-stick cookware containers, either in the container as initially purchased by the consumer, in the consumption of aluminum over the cooking lifetime of the consumer, or both.
In the present invention, a removable and replaceable infix or insert member is provided which may be readily replaced when the non-stick coating has deteriorated after its normal useful life of 2 to 3 years, rather than necessitating disposal of the entire container at that time as in the past. The infix member of the invention is not relied upon to provide any substantial amount of the requisite strength of the container and, thereby the relatively expensive aluminum from which the infix member is formed may be substantially reduced in thickness and quantity. The principal requirement of the infix member and its composition is that it be a compatible substrate for the bonding of the non-stick coating, e.g. aluminum and PTFE respectively. In turn, a permanent, highly durable exterior cartridge or shell member, into which the infix member is positioned during use, is relied upon to provide in predominant measure the structural and thermal prerequisites of the container and its aesthetic appearance. This cartridge member is constructed so as to be highly durable and to last the lifetime of the consumer and be rechargeable with a new infix member once the non-stick performance of the coating has deteriorated to an unacceptable level.
Thus, the initial expense to the consumer of the cookware container of the present invention may be substantially reduced by the use of a ferrous metal, such as carbon steel, in the cartridge member, the latter material being relatively inexpensive compared to aluminum. Moreover, such ferrous steels not only are relatively inexpensive, but also display several advantages over aluminum, including strength, resistance to high temperatures and weldability to mention a few, and also are compatible for use with well known decorative and protective coatings, such that the resulting cartridge is extremely durable and attractive. Even if the exterior cartridge or shell member or the closure of the cookware unit is formed of a more expensive material than carbon steel, such as aluminum, metal laminates, or stainless steel, the consumer will still realize a substantial saving over his cooking lifetime, since only the thin infix member need be discarded and replaced upon deterioration of its non-stick coating, rather than the entire cookware container as in the present state of the art.
In passing, it should be noted that any reduction in the intial fabrication cost of a cookware unit results in a substantial reduction in the ultimate initial purchase price to the consumer. This becomes particularly evident when it is considered that the retail consumer not only must bear the initial cost of fabrication of the product, but also the substantial overhead and the markup throughout the fabricating, marketing and advertising levels, as well as the sales level, both wholesale and retail. Since these markups, which must cover the overhead and profit throughout the commercial chain are based upon a given percentage of respective costs, any saving realized in the fabrication of the product will usually be substantially compounded by the time the product reaches the consumer.
In addition to the savings in material expenses afforded by the separability features of the container of the present invention, such separability also renders possible the performance of certain processing steps performed upon the respective components of the container, which can not otherwise readily be performed on containers of the present state of the art without probable adverse effects.
The handle of cookware containers can not be attached directly to the container, since the thermal expansion and contraction of the handle during use will loosen the seal between the interior side wall and the head of the handle fastener and result in leakage. However, in the present invention, the handle may be directly affixed to the cartridge without studs or other auxiliary connections. Leakage will not develop since the head of the handle fastener may be positioned between the interior of the cartridge and the exterior of the infix member in an area which is not exposed to contact with the food content. Also if spot welding is to be performed upon a conventional container, such as in the affixation of the handle, such welding would raise the temperature of any previously applied non-stick coating to a level at which this coating would decompose. Moreover, if the handle is riveted to conventional non-stick utensils, the metallic head of the rivet will be exposed to the food directly and caking will occur on these heads which necessitates abrasive action for removal. Such abrasion accelerates the deterioration and frequently damages the non-stick coating in the vicinity of the rivet heads and thus renders the container unsuitable for non-stick use in a short time. If cleaning of rivet heads with metallic or other abrasive means is not performed, the food components which settle between the rivet head and the non-stick coating may result in objectionable odors, inconvenience, and under extreme conditions, health hazards. In contrast to these shortcomings, the handle of the cookware unit of my invention may be riveted or bolted to the cartridge of the container without risk of damage to the non-stick coating from cleaning because the infix member of the container prevents the food content from contacting the rivet or bolt heads and prevents leakage due to thermal deformation of the handle. Moreover, since the infix insert and cartridge member of the present invention are separable, welding may be readily performed upon the exterior of the cartridge shell in the absence of the infix member without risk of damage to the non-stick coating of the infix member.
In conventional cookware containers, the handles are usually formed of a heat insulative organic composition, such as a phenolic resin or wood, in order to prevent burns while handling the container. Since such materials are somewhat combustible, and in any event subject to decomposition from flame impingement, flame protection of the handle has frequently been provided in the form of a separate ferrule or the like which is fitted over the end of the handle adjacent the container. In the cookware unit of the present invention, the flame protection component may be formed as an integral part of the container eliminating the need for expensive, separate components for this purpose. Moreover, integration of the flame protector with the container is facilitated by the novel infix member construction of the present invention which provides a smooth continuous container rim.
Also, in the present state of art, stainless steel and its laminates are known to offer certain advantages in hygiene, cleanability and aesthetic appearance when employed in a cookware unit. Nevertheless, stainless steel and its laminates are poor heat conductors and thus facilitate the excessive accumulation of heat which tends to burn and cake the food. In order to prevent this, most stainless steel cookware containers include a heat dissipating bottom exterior. Such bottom exterior may be copper or aluminum which may be welded, soldered, electrolytically coated or deposited by other known means onto the exterior of the container bottom. Thus, great care and expense are involved in maintaining a suitable aesthetic appearance of the cookware in view of this visible addition to the bottom. Also added fabricating costs and care are necessary to insure the cleanability of this exterior bottom addition which is not only in direct contact with flame, but also is exposed to contamination by overflowing food and water and various detergents in the sink or dishwashing machine. Moreover, detergents which may be compatible with stainless steel may not always be compatible with copper and aluminum and any recess or crevice in the attachment of the exterior bottom addition impedes the cleanability of such utensil. In contrast, the container of the present invention permits the incorporation of an interior member to facilitate heat dissipation in the container bottom and to prevent the thermal deformation or buckling of the container bottom due to repeated expansion and contraction from repeated heating and cooling. The buckling of the container bottom is particularly detrimental to heat transfer where a hot plate is the heat source, since hot plate cooking is convenient and effective only so long as the bottom of the cookware is flat so as to maximize contact with the hot plate, heat transfer being primarily effected by conduction in such hot plates. However, deformation or buckling of the bottom of the utensil will result in air gaps between the hot plate and the container and thus reduce the effectiveness and economy of heat transfer. The likelihood of such buckling or deformation will be substantially reduced in the present invention, since an inexpensive carbon steel member may be placed in the interior bottom of the cartridge member. Since the interior of the cartridge is never exposed to food, the method of placement of this member need not take into account cleanability. Also, since the bottom member is placed in the interior of the cartridge member, it will not be visible and the aesthetic appearance of the container will not be impaired. It is evident that both of these factors will reduce the labor cost of fabrication, in addition to the saving realized by the use of inexpensive carbon steel, rather than expensive copper or aluminum.
Finally, since the cartridge and infix members are formed as separate components, they may also be constructed such that they are spaced somewhat from each other in the finally assembled cookware container, thereby readily diffusing the heat which flows through the container to prevent hot spotting and/or loss of heat from the food being prepared through the side walls of the container, as well as thermal deformation of the container.
In summary, a cookware unit constructed in accordance with the principles of the invention renders possible the realization of at least several or all of the following advantages.
The performance of one or more highly desirable or economical fabricating steps upon either the cartridge shell or infix insert or closure member by themselves which could not be otherwise readily performed on prior cookware, may be readily performed on the cookware unit and on its individual members of the present invention.
A substantial reduction is realized in the cookware unit of the present invention in the usage of expensive materials, such as aluminum, stainless steel, laminates thereof, etc., and in expense to the consumer over the prior non-stick cookware containers, either or both in the initial manufacture or during the consumer's lifetime.
Enhanced welding and riveting qualities and integral affixation and flame protection of handles are realized in the present invention.
Pollution due to metal scrap waste, handles, closures and packaging therefor is substantially reduced, since when practicing the principles of the present invention, only the thin infix insert will become scrap and not the entire cookware unit, as in the past.
The container constructed in accordance with the principles of the present invention is capable of an aesthetic pleasing appearance, even though the usage of expensive materials is substantially reduced.
The infix or insert member of the present invention may be replaced either by the individual consumer or by a service facility, as desired.
The thermal performance of a container constructed in accordance with the principles of the present invention is substantially improved thereby effecting a substantial reduction in the possibility of hot spotting in that portion of the container which is to be exposed to the heat source. Such hot spotting might result in decomposition of the non-stick coating which, in turn, would cause destruction of the coating and the generation of potentially toxic vapors. The thermal performance of the container also substantially reduces the likelihood of burning-on of the food which is to be prepared in the container, the latter of which is not only undesirable from the standpoint of damage to the food being cooked, but also generally necessitates the scraping of the container to remove the burned food and consequent damage to the non-stick coating.
Due to the improved thermal performance of the cookware container incorporating the principles of the present invention, the likelihood of thermal deformation between the bottom and side walls of the cookware container is also substantially reduced. Such deformation generally occurs as the result of undesirable temperature gredients which result from unequal conduction through the container walls so as to cause buckling of the side walls and/or bottom walls of the container. Such buckling is not only undesirable from an aesthetic standpoint, but also, where the container is to be employed on a hot plate heat source where the transmission of heat to the container from the heat source depends primarily upon conduction, such deformation will result in inefficient heat transfer.
Moreover, the improved thermal performance of the container of the present invention may be realized without employing thick expensive materials of construction or cladding and plating manufacturing techniques as in the past.
In a principal aspect of the invention, a cookware unit constructed in accordance with the principles of the present invention includes heat conductive cartridge means and infix means, both of which are of a substantially predetermined configuration and which define cavities therein. The infix means is removably positioned in the cavity of the cartridge means and an easily cleaned coating is provided on the infix means. Fastening means removably attaches the cartridge means and the infix means together into an integral container.
These and other objects, features and advantages of the present invention will be more clearly understood from a consideration of the following detailed description.